Initial automatic channel selection implementation
Luis R. Rodriguez
mcgrof
Thu Jun 2 22:23:24 PDT 2011
On Thu, Jun 2, 2011 at 4:49 PM, Felix Fietkau <nbd at openwrt.org> wrote:
> On 2011-06-03 12:36 AM, Luis R. Rodriguez wrote:
>>
>> On Thu, May 26, 2011 at 5:59 PM, Luis R. Rodriguez<mcgrof at gmail.com>
>> ?wrote:
>>>
>>> ? What I'd like to do is to affect the ratio to nullify it if the noise
>>> ? is very low on the channel. Given that noise is logarithmic we'd have
>>> ? to use a logarithmic function as well. Working on that now.
>>
>> OK I've figured a way to plug the noise into this, I designed the
>> following function we can use as a factor:
>>
>> 1.1^(x+110)
>>
>> Wolfram|Alpha boring details of this function:
>>
>> http://bit.ly/mJNXE9
>>
>> x,y results of different noise values in dBm, using apcalc:
>>
>> mcgrof at tux ~ $ calc
>> C-style arbitrary precision calculator (version 2.12.3.3)
>> Calc is open software. For license details type: ?help copyright
>> [Type "exit" to exit, or "help" for help.]
>>
>> ; define f(x) = 1.1^(x+110)
>> f(x) defined
>>
>> ; f(-130)
>> ? ? ? ?~0.14864362802414368640
>> ; f(-120)
>> ? ? ? ?~0.38554328942953174736
>> ; f(-119)
>> ? ? ? ?~0.42409761837248492210
>> ; f(-118)
>> ? ? ? ?~0.46650738020973341431
>> ; f(-117)
>> ? ? ? ?~0.51315811823070675574
>> ; f(-116)
>> ? ? ? ?~0.56447393005377743132
>> ; f(-115)
>> ? ? ? ?~0.62092132305915517445
>> ; f(-114)
>> ? ? ? ?~0.68301345536507069189
>> ; f(-113)
>> ? ? ? ?~0.75131480090157776108
>> ; f(-112)
>> ? ? ? ?~0.82644628099173553719
>> ; f(-111)
>> ? ? ? ?~0.90909090909090909091
>> ; f(-110)
>> ? ? ? ?1
>> ; f(-109)
>> ? ? ? ?1.1
>> ; f(-108)
>> ? ? ? ?1.21
>> ; f(-107)
>> ? ? ? ?1.331
>>
>> So then, we'd use a frequency for initiating beaconing (AP, Mesh, P2P)
>> which uses the lowest value from the following computation:
>>
>> (busy time - tx time) / (active time - tx time) * 1.1^(noise + 110)
>>
>> The 1.1 factor can be modified more accurately to represent the
>> exponential factor of how noise should affect interference decisions,
>> the 110 value here can be modified for any other arbitrary value we
>> find as representative of a regular noise value from a simple AP on
>> the frequency we are observing, my assumption here was -110 dBm.
>
> -110 dBm is not a real noise value. It's an unrealistic, ath9k-specific
> value. I have a patch that changes ath9k to make noise and signal strength
> values more realistic, and I'll submit it soon, as soon as I've made it a
> bit more precise.
Nice. As I noted though this value is arbitrary for now, we can change
it at will. Any other feedback? If not I'll start hacking on it.
Luis
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